18.2.1 Guidelines for Sizing Volumes

NSS volumes are logical storage media that acquire space from pools of storage. When you create a logical volume, you can either assign it a fixed quota as the maximum size, or allow it to expand to the pool size. To grow a volume, you might need to add new segments to grow the pool first, up to the maximum pool size of 8 TB.

If a pool contains multiple volumes, the cumulative administrative maximum sizes of all volumes can exceed the pool’s maximum size by overbooking, although real total size is bound by physical limitations. Because space is allocated to volumes as needed, a volume might not reach its quota. As the overbooked volumes consume the available physical space, you need to add more disk space to the pool to accommodate the growth, or consider moving or splitting volumes to move data to other pools.

For example, suppose you have an 800 MB storage pool with eight volumes set at 100 MB each. The administrative size equals the physical limits. To overbook the pool, you can add volumes, set one or more of the volumes to expand to the pool size, or increase the size of existing volumes, with the understanding that these are administrative maximum sizes, not physical sizes.

Because volume sizes can be overbooked in a pool, NSS automatically considers what space is remaining in a pool in order to report the maximum size that is currently possible for the volume. In addition to other volumes that can consume space in a pool, NSS snapshots and third-party snapshots can consume space that might not be reported in all of the management tools that report space. NSS reports the total space possible for the volume and the amount of space used by the volume so that tools can properly calculate the maximum free space available.

18.2.2 Guidelines for Name Spaces

NSS recognizes DOS, Macintosh, UNIX, and Long name spaces. Volume names, directory names, and filenames in NSS are case insensitive. This differs from Linux POSIX file systems, which are case sensitive by default. For information, see Lookup Namespace.

18.2.3 Guidelines for NSS Volumes in a Cluster

You must create at least one shared volume in a cluster-enabled pool. Typically, all volumes are created when you initially set up the cluster resource and before you need to cluster migrate or fail over the resource to other servers in the cluster.

The Server, Pool, Volume, Cluster Resource, and Cluster objects are recommended to be in the same context (such as ou=ncs,o=novell).

If the objects are in different contexts, you might receive an eDirectory error when you attempt to modify the pool, create or modify the volumes, home directories, Distributed File Services junctions, or any other elements that are managed using eDirectory objects. To resolve the problem, you must cluster migrate the pool cluster resource back to the node where the pool was created in order to perform those management tasks.

18.2.4 Guidelines for NSS Volumes in a Mixed-Node Cluster

In a clustered storage area network with Novell Cluster Services, NSS volumes can fail over between kernels, allowing for full data and file system feature preservation when migrating data to Linux. However, you cannot SAN boot cross-platform.

For information about using NSS volumes cross-platform, see the following: